Janet Jackson reminded us who’s the real idol on the season finale of “American Idol.” Ms. Jackson, sporting a short, slicked-back cut, appeared onstage in a flowing black and red dress to sing her ballad “Nothing.” She then stripped down to an eye-popping bodysuit to perform her 1986 classic “Nasty.”

Christina Aguilera also joined this season’s female contestants on her hit “Fighter,” plus a solo version of her Bionic ballad “You Lost Me.” Season 3 champ Fantasia returned with her fellow “Idol” winners to help say goodbye to Simon Cowell on his last show.